542 Wisconsin Academy of Sciences, Arts, and Letters. 
appear. As conidia were taken from the varieties of squashes^ 
pumpkins and gourds shown in the table these results indicate 
clearly that the mildew on the cucumber is the same as that 
which occurs on the other cucurbits. 
In the course of these experiments, twenty-three different 
varieties of commonly cultivated cucurbits were used. These 
belonged to five different species representing the three genera 
Cucurbita, Cucumis and Lagenaria. Each of these types was 
readily infected when inoculated with the conidia taken from 
any other. There was no difference in the infecting power of 
the mildew on the different species and genera, the fungus 
readily passing from plants of one genu’s to plants of either of 
the others. 
The control plants kept in most of the experiments remained 
entirely free from the mildew except in two experiments. In 
experiment 9 a small patch of mycelium was observed upon 
the stem of the control. As one of the cotyledons of the inocu¬ 
lated plant was in contact with the stem of the control at the 
point of infection, it is likely that some of the conidia placed 
upon the cotyledon were washed down upon the stem of the 
control and caused infection. In experiment 76, a small in¬ 
fected area was present on the control cotyledon This was 
underneath an inoculated leaf, and probably some conidia were 
washed down upon it. 
Young plants were used in all of my experiments, and the 
question may be raised whether seedlings are not more suscep¬ 
tible to the fungus than mature plants. Interesting collateral 
evidence, however, was observed on this point. Several vines 
of cucurbits, especially squashes and ornamental gourds, grew 
to maturity in the greenhouse, and the mildew spread over all 
these. It at first spread more slowly on the gourds, but later 
these also were covered with the white patches of mycelium, pro¬ 
ducing immense quantities of conidia. In the light of my ex¬ 
periments, there can be no question but that it was the same 
mildew which attacked all the vines. 
These results are in striking contrast to those previously ob¬ 
tained with the mildews on other host plants. In the light of 
